A prior patent document (Korean Patent Publication No. 10-2003-0004975) relates to an intelligent unmanned mail acceptance system that executes, for post offices, stamp sale work and various mail receipt works, such as general mails, registered mails, express mails, and international mails, and public relations work by using high-tech image recognition and mechatronics technology. A customer inserts a general mail or a small parcel mail (which is desired to send) through an automatic door, and when the customer selects a desired kind of post service by using a touch screen, by using two CCD cameras based on a stereo type, the intelligent unmanned mail acceptance system automatically measures a weight and size of a mail, calculates postage on the basis of the measured weight and size of the mail, and displays the customer's selections and the calculated postage to the customer.
When the customer pays for the displayed postage with coins, bills, or a card, the intelligent unmanned mail acceptance system printing-outputs a label that indicates a stamp substitute charge stamp, an express mail, or a registered mail. When the customer attaches the printing-output materials to the mail and again inserts the main with the printing-output materials attached thereto, the mail is automatically and finally inserted into a mail storage box included in the intelligent unmanned mail acceptance system.
The intelligent unmanned mail acceptance system is used as a method in which a weight of a mail is measured by a general scale, postage is calculated based on the measured weight, and the mail is received. The intelligent unmanned mail acceptance system uses a method in which a width value and height value of an upper surface of a mail are calculated based on four corner points by using two or more image cameras, for measuring a size of the mail. Also, when an image of a side surface is accurately acquired, a calculation result of a height value can be provided. A body of an intelligent unmanned mail acceptance apparatus has a size in which a front width is 1,900 mm, a front height is 1,800 mm, a front and rear depth is 800 mm, and has a self-supporting structure which is configured with three parts such as a left part, a central part, and a right part. Considering the width of total 1,900 mm, a width and height of a central part, and a size of a mail inserting port, the intelligent unmanned mail acceptance system receives only small mails (depth of about 270 mm*width of about 180 mm*height of about 150 mm), and two or more cameras are installed in an upper space for measuring a height of a mail.
Moreover, the intelligent unmanned mail acceptance system needs a large space for installing two or more cameras used to measure a size of a mail. Also, since the intelligent unmanned mail acceptance system combines acquired images to calculate a size of a mail, much time is expended, and a large error of a size measurement result occurs due to the size of the mail and qualities of the acquired images.
That is, the intelligent unmanned mail acceptance system cannot accurately measure sizes of various mails in a small space.